This project involves a comprehensive genetic analysis of the regulation of cardiolipin biosynthesis in yeast. A search will be conducted for structural and regulatory mutants affecting this pathway. These newly isolated mutants, as well as existing mutants of phospholipid, sterol, and fatty acid synthesis will be used to analyze the cardiolipin pathway and to ascertain the role of cross-pathway control in the regulation of cardiolipin synthesis. Molecular technology will be employed to clone the genes involved in this pathway in order to establish gene:enzyme relationships, to analyze the role of transcriptional control in the regulation of the pathway, and to identify crucial regulatory sites within the structural genes. The structural and regulatory mutants will be used to study the role of cardiolipin in the development of mitochondria and in the activities essential for mitochondrial function. The information gained in these studies will provide insight into the regulation of membrane biogenesis and the role of phospholipid regulation in the development and function of a complex subcellular organelle. Yeast is amenable to genetic, molecular, and biochemical analyses and is itself a eukaryote which systhesizes cellular and mitochondrial membranes by pathways similar to those of higher organisms. The mitochondrion is a complex organelle which plays a key role in energy metabolism and phospholipid biosynthesis, and is furthermore implicated in processes leading to cellular senescence. The study of mitochondrial membrane biogenesis in this model eukaryote may thus be expected to contribute to our understanding of the role played by the mitochondrion in these processes.